1. Technical Field of the Invention
The invention relates generally to communication devices; and, more particularly, it relates to connectivity of the various components and circuits within such communication devices.
2. Description of Related Art
Data communication systems have been under continual development for many years. Within such communication systems, there are many communication devices included therein that that include various integrated circuits, chips, modules, and functional blocks. These communication devices may be transceivers, transmitters, receivers, or even other peripheral type devices. Within these communication devices, various chips (e.g., sometimes referred to as integrated circuits, packages, encapsulated chips, and so on) are typically mounted on a PCB (Printer Circuit Board) and are typically communicatively coupled via the PCB to other chips that are mounted thereon. The manner in these various chips communicatively couple to the PCB can introduce some serious deficiencies to the overall communication device's performance. Moreover, even within the actual chips within these communication devices, the manner in which the various circuitry portions therein are communicatively coupled to one another may also introduce serious deficiencies to the overall communication device's performance. In many instances, differential type signals are employed within such communication devices for performance considerations such as noise immunity. As such, there is oftentimes a need to perform transformations to and from differential signals and single-ended signals. That is to say, there is often a need to transform a signal from a differential signal type to a single-ended signal type and vice versa. To perform this conversion from a signal from a differential signal type to a single-ended signal type, the circuitry of the communication device will typically employ a balun (i.e., a balanced/unbalanced transformer). That is to say, within an integrated circuit, a communication approach by which this transformation (e.g., differential to single-ended) is performed is to use a balun within the circuitry of a chip. The balun is typically implemented as a transformer on the chip whose windings are actually implemented on the die of the chip.
Until very recently, these baluns were implemented as being off-chip, i.e., on the PCB (Printer Circuit Board), and they were typically implemented in the form of micro-strip lines. More recent attempts to integrate a balun onto a chip have met with some serious performance limitations. For example, parallel winding, inter-wound winding, overlay winding, single planar, square wave winding, and concentrical spiral winding on-chip baluns have been tried with limited success. Each of these on-chip baluns suffers from one or more of: low quality factor, (which causes the balun to have a relatively large noise figure); too low of a coupling coefficient (which results in the inductance value of the balun not significantly dominating the parasitic capacitance making impedance matching more complex); asymmetrical geometry (which results in degradation of differential signals); and a relatively high impedance ground connection at the operating frequency.
Moreover, in the wireless communication system context (e.g., RF (Radio Frequency) communication systems), these integrated circuits have met with limited success larger in part to the manner in which they are implemented. In addition, within higher power applications, the size of the balun on the die can itself introduce some significant problems. This is largely because the size of the tracks of the transformed balun to support these higher power applications is implemented using relatively wider tracks and this inherently requires a larger spatial area on the die.
FIG. 1A is a diagram illustrating a prior art embodiment of a single transformer balun (having relatively wide tracks) within an integrated circuit (shown using a side view). As shown in this embodiment, a chip (e.g., which may alternatively be referred to as an encapsulated chip, package, an integrated circuit, or other terminology) typically includes a die (e.g., a silicon substrate) on which a certain amount of circuitry is emplaced. This circuitry may be referred to as on substrate circuitry. One portion of the on substrate circuitry may be a single transformer balun that is implemented as a transformer as described above. To support higher power applications, such a single transformer balun may be implemented using wound tracks on the substrate. The windings (shown as a winding 1 and a winding 2) are separated by a dielectric insulating layer, and the magnetic coupling between the windings operates as a transformer.
FIG. 1B is a diagram illustrating the same prior art embodiment of a single transformer balun (having relatively wide tracks) within an integrated circuit (shown using a top view). This embodiment shows a side view of the very same components as within the previous diagram. As can be seen, a chip may have several (sometimes hundreds or even more) or pins around the periphery of the chip. Each of these pins on the chip may communicatively couple to a PCB pad or trace for subsequent coupling to another location either on this same PCB or to another location.
Again, for higher power applications, the windings of the balun transformer are typically implemented in the prior art using relatively wider tracks. This increase in size is largely because of the need to use higher currents, to support lower input impedances (Zin), and so on. However, this inherently requires that a larger area on the die is dedicated to the balun (given the wider and thicker tracks employed). The efficiency of the balun also reduces when a very wide balun transformer arrangement is employed; this is largely because the actual winding of the balun transformer become further and further apart thereby reducing the communicatively coupling between the windings of the primary and secondary of the balun transformer. Tightly coupled relatively thinner tracks (as in a low power balun transformer) offer a high degree of operational efficiency, in that, a high degree of electromagnetic coupling may be achieved. The further apart the tracks are, then the lower the degree of electromagnetic coupling may be achieved. The use of these relatively wider tracks, as employed within higher power applications, inherently results in a component having windings that are relatively further apart and therefore have a lower degree of electromagnetic coupling between them.
In addition, this problem can be exacerbated when the integrated circuit operates within a communication device that operates within a wireless communication system.
Looking at one example of a WLAN (Wireless Local Area Network) communication system operating according to one of the IEEE (Institute of Electrical & Electronics Engineers) 802.11 standards or recommended practices whose RF (Radio Frequency) carrier frequency, f, is within the 2.4 GHz (Giga-Hertz) frequency range, these relatively large track windings employed within such a transformer balun can operate as an antenna with respect to the wireless communication existing therein. This can lead to a great degree of interference.
As can be seen, there are many serious deficiencies when using a prior art approach of wide track balun transformers within integrated circuits. A great deal of interference and reduction of performance of the communication device may be experienced when using these prior art approaches. Clearly, there is a need in the art for a more effective and efficient way of performing the conversion between differential and single-ended signals, particularly within the high power and wireless communication system contexts.